In modern rapid transit vehicles, such as railway vehicles, the braking and propulsion controls are often effected by a master controller. These master controllers typically include an operator interface, such as a handle, which can be moved from a neutral or coast position to either a propulsion or braking position to provide a control signal throughout the vehicle. Two additional controls are also commonly coupled to the operator interface on a master controller, a key switch and a direction switch. The key switch can be placed in one of several positions, which typically include an off, run, and special charge position. There may be fewer or additional positions, and the name for each position may also differ. The direction switch can either be in a locked position (neutral) or in one of two operational positions (left and right). The key switch is used to allow the master controller to function, and the direction switch is used to select the vehicle's desired direction (forward or reverse).
Recent master controller construction techniques include an operator's interface, such as a handle, which is connected to a cam that operates a series of microswitches or position sensors. These microswitches or sensors, in certain conditions, operate motor control relays. It is desirable, however, to prevent the operation of the key switch or the direction switch in certain configurations of the handle position. Should the switches be operated in an undesired configuration, the vehicle could be turned off without application of the brakes; the direction of the vehicle could be changed while the operator interface (handle) is in a propulsion position; or in the special charge mode (or test mode), the brakes must be applied or an operator or inspector could be injured should the vehicle move. Thus, it is an object of the present invention that undesired operation of the master controller be prevented.